1. Field of the Invention
The present invention relates to shoulder surgery. More particularly, the present invention the relates to surgical processes whereby the head of the humerus receives a resurface implant that thereon. Additionally, the present invention relates to surgical process whereby the head of the humerus is removed and reattached during the process of applying the resurface implant.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
The shoulder joint, the largest joint in the upper extremity, functions as the fulcrum for all functional activities of the upper extremity, and also affords the greatest range of motion and planes of motion of any joint in the body. These unique characteristics of relatively high force transmission as well as the large range of motion afforded by the unique anatomical structure of this joint, impart certain difficult considerations in total shoulder prosthetic design. The design must allow for the shoulder to be the foundation joint for the upper extremity with its large range of motion as well as for the limited osseous framework available for fixation of the device. Additional considerations include the proximity of neural and vascular anatomic structures, the usual difficult surgical approach to the shoulder secondary to major muscular structures, and the relationship of the acromiom to the gleno-humeral articulation.
Much prior prosthetic replacement development has been directed at the hip and knee joints, the major weight bearing joints of the lower extremity. However, these joints have a much less complex and extensive range of motion and the anatomical considerations in these joints, especially the hip, are much less complicated than the shoulder. The surgical approach to the hip and the knee is generally considered less demanding than the surgical approaches to the shoulder joint.
Of the several surgical options available for the painful shoulder with limited or no motion, gleno-humeral replacement, commonly accepted as total joint replacement for the shoulder, has offered the best solution for problems of the entire shoulder joint to date. At present, there are two basic categories of prosthesis available. These include constrained prosthesis and essentially unconstrained prosthesis. The major problems with the constrained prosthesis occur as in all constrained prosthesis, i.e., limited motion, mechanical failure, and loosening. In the unconstrained category, the prosthesis usually available utilizes surface or flush glenoid components with fixation devices directed to the anatomical cancellous region of the scapulae. Fixation of the glenoid component has and continues to be considered a problem. Incomplete recovery of range of motion primarily in abduction and forward flexion has been encountered and appears to be related to overall prosthetic design. Another problem area in the present gleno-humeral replacement is proximal subluxation of the humerus with resulting humeral acromial impingement.
The conventional techniques of shoulder replacement surgery requires surgical transection of a rotator cuff to gain sufficient exposure of the joint surfaces of the shoulder. After the joint surfaces are replaced, the rotator cuff tendon must be surgically repaired with suture material. This tenuous repair necessitates an obligatory period of approximately six weeks for the rotator cuff tendon to heal before advanced shoulder rehabilitation can be performed. This surgical transection and subsequent repair, as well as the delay in rehabilitation, hold significant consequences for the functional outcome of the shoulder replacement including permanent weakness and decreased range of motion.
Additionally, despite the extensive exposure, conventional methods for shoulder replacement surgery still fail to properly restore the native anatomic relationships of the joint surfaces of the shoulder. Conventional methods prepare the humeral surfaces of the shoulder joint by referencing off the intramedullary axis of the humeral shaft. This poses great difficulty for the surgeon since the intramedullary axis has an inconsistent relationship to the humeral surface. The humeral joint surface also possesses a complex anatomy with significant variability which cannot be entirely restored with conventional methods and implants. There exists much variability in the humeral head neck-shaft angle, posterior and medial offset, version (rotation), height, thickness, and radius of curvature. The failure to restore the native anatomic relationships and biomechanics to the shoulder joint has proven to result in a significantly lesser functional and durable outcome
Conventional methods of shoulder replacement surgery also have difficulty gaining access to the glenoid joint surface. The glenoid surface of the shoulder joint is best prepared by working along an axis perpendicular to its surface. Because the humeral head sits in the way, this is a nearly impossible task with conventional methods. The humeral head has to be partially removed, the subscapularis (anterior shoulder rotator cuff muscle) transected, and the proximal humerus dislocated to even get close to working along this axis. Because of this difficulty, a majority of orthopedic surgeons still choose not to replace the glenoid surface despite clinically proven results of improved pain relief and function for shoulder replacement surgery when both the humeral and glenoid surfaces are replaced.
In these prior processes for the resurfacing of the head of the humerus, various jigs are utilized so that the resurface implant is properly applied over the head of the humerus. Typically, these jigs will extend outward referencing off the intramedullary axis of the humeral shaft, so as to provide a surface extending over the head. It is known that there is a great deal of variation in human beings between the orientations between the humeral head and the humeral shaft. Additionally, many surgeons have a great deal of difficulty in attempting to properly align the jig so that the resurface implant is properly applied onto the humeric head. Since the quality of surgeons varies greatly, inexperienced or less capable surgeons will often have a great deal of difficulty in properly orienting the resurface implant with the humerus. Additionally, the variations in anatomical structures will also cause a great deal in variation in the ability to properly place the resurface implant onto the head of the humerus. As such, a need has developed so as to orient the resurface implant in relation to the head of the humerus rather than in relation to the intramedullary axis of the humeral shaft.
In the past, various patents have issued relating to surgical process and apparatus for the resurfacing of the humeral head. For example, an early patent is that of U.S. Pat. No. 4,550,450, issued on Nov. 5, 1985 to J. G. Kinnett, provides a total shoulder replacement arthroplasty system which encompasses replacement of the articular surface of the humerus and adjacent glenoid articular surface with a humeral component having a convex surface and a shallow trapezoidal fixation keel to avoid violation of the medullary cavity by the prosthesis and with a concave overmounted glenoid component having a similar keel. The inferior aspect of the acromion is resurfaced with an acromial component for replacement of the acromial clavicular joint so as to provide the mechanical advantage of a fulcrum for abduction and forward flexion of the humerus.
U.S. Pat. No. 7,585,327, issued on Sep. 8, 2009 to M. A. Winslow, provides a resurfacing implant having a head and an extended articulating surface protruding from a portion of the head. This resurfacing implant is operable to articulate with at least one of a bone and a ligament. The head has an exterior articulating surface, an interior surface opposite the exterior articulating surface, and an anchoring device extending from the interior surface.
U.S. Patent Publication No. 2010/0292802, published on Nov. 18, 2010 to K. Borowsky, provides a shoulder replacement prosthesis that has a head for replacing the humeral head and a connection shaft. The head has a domed portion and a flange positioned at an end region of the domed portion. The flange has a width which varies around the domed portion. The flange has a greater width at a part corresponding to a region of the greater tuberosity than at a part corresponding to a region of the lesser tuberosity. The flange is provided with a plurality of connection portions for securing the tendons attached to the tuberosities. By dimensioning the flange appropriately, the anatomical positioning of the tendon-to-bone connections can be more accurately replicated.
U.S. Patent Publication No. 2004/0034431, published on Feb. 19, 2004 to Maroney et al., discloses a modular prosthetic assembly for use during performance of a shoulder replacement procedure on a patient. The modular prosthetic assembly includes a stem component configured to be implanted into a medullary canal of a humerus of the patient. The assembly also includes a prosthetic head component configured to be secured to a proximal end portion of the stem component. The prosthetic head component has a glenoid-bearing portion which is configured to bear against a glenoid surface of a scapula of the patient when the stem component is implanted into the medullary canal of the humerus of the patient and the prosthetic head component is secured to the stem component. The prosthetic head component also includes an acromion-bearing portion which is configured to bear against an acromion of the patient during abduction of the humerus when the stem component is implanted into the medullary canal of the humerus and the prosthetic head component is secured to the stem component.
U.S. Patent Publication No. 2006/0009852, published on Jan. 12, 2006 to Winslow et al., provides a two-piece humeral component for use in joint arthroplasty which is adapted to be implanted into a joint and engaged by a socket component of the joint. The joint component includes a body having a first articulating surface and a second medial surface opposite the first articulating surface. The first articulating surface is adapted to be engaged by the socket and the second medial surface is adapted to be secured to mounting portion. The mounting portion has a first surface and a second medial surface. The first surface is adapted to be fixably engaged to the second mounting portion of the humeral component. The second medial surface is adapted to be secured to the humerus.
U.S. Patent Publication No. 2005/0043805, published on Feb. 24, 2005 to S. C. Chudik, teaches a method and devices for shoulder replacement surgery that spares the rotator cuff. The method utilizes two anterosuperior passages to gain access to the glenohumeral joint, neither of which requires transaction of the rotator cuff. In addition, a transhumeral portal created through the second anterosuperior passage for use as a working tunnel. U.S. Patent Publication No. 2007/0016304, published on Jan. 18, 2007 to S. C. Chudik, shows a similar process and apparatus shoulder replacement surgery.
U.S. Patent Publication No. 2008/0021564, published on Jan. 24, 2008 to S. B. Gunther, describes a monoblock (non-modular) humeral head resurfacing implant designed to replace a portion of the patient's humeral head. The implant is designed to be performed either as a hemiarthroplasty or as a component of a total shoulder replacement along with a standard glenoid or inset glenoid implant.
U.S. Patent Publication No. 2011/0313533, published on Dec. 22, 2011 to S. B. Gunther, shows a humeral head resurfacing implant that comprises a body having an exterior articulating surface having a substantially hemi-spherical or elliptical shape, and an interior surface opposite the exterior articulating surface. The exterior articulating surface is capable of articulating with a glenoid of a patient. The interior surface includes a solid anterior portion that comprises a planar support surface for supporting the implant against a humeral head of the patient. The solid anterior portion fills at least 20% of the internal volume of said body. A stem portion extends outwardly from a central point within the interior surface.
It is an object of the present invention to provide a surgical process for the resurfacing a humeral head which assures the proper placement of the resurface implant in accordance with the natural anatomical structure of the patient.
It is another object of the present invention to provide a surgical process for the resurfacing a humeral head that creates more working space for the surgeon for the purposes of resurfacing and repairing the glenoid.
It is another object of the present invention to provide a surgical process for the resurfacing a humeral head that avoids the use of complicated jigs that are oriented to intramedullary axis of the humeral shaft.
It is a further object of the present invention to provide a process for the resurfacing a humeral head that allows surgeons of varying levels of skill to properly install the resurface implant.
It is a further object of the present invention to provide a surgical process for the resurfacing of a humeral head which assures that the resurface implant is securely positioned over the humeral head and imbedded within the humerus.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.